Why you should care

The Kavanaugh Effect is showing signs of denting the blue wave. With Republicans newly energized by the fight to get Brett Kavanaugh on the Supreme Court, OZY’s exclusive election prediction model in partnership with data firm 0ptimus this week shows their chances improving in the battle for control of Congress — though Democrats remain favored by a substantial margin to retake the House.

Democrats have an 86.4 percent chance to control the House next year, with our model now projecting the Dems to hold 227 seats — clearing the 218 needed for a majority. “With four weeks to go, Republicans are still unlikely to maintain control of the House, though there are signs of life this week,” says Alex Alduncin, data scientist for 0ptimus.

The numbers improved for the GOP over the past week, as the emotionally charged fight over Kavanaugh’s nomination reached a crescendo.

Meanwhile, Republicans have an 89.9 percent chance — the “high-water mark,” Alduncin points out, since we launched the model last month — of holding a Senate majority of at least 50 seats. Republicans are projected to gain one seat overall, a 52–48 margin.

In partnership with the Republican technology and data firm 0ptimus, we crunched more than 100 factors that helped predict past elections, with extra weighting for unique aspects of this political year, to produce these forecasts. For more on how these numbers were derived, scroll down to the box below. For more exclusive election coverage, subscribe to our Midterms in a Minute newsletter.

The numbers improved for the GOP over the past week, as the emotionally charged fight over Kavanaugh’s nomination reached a crescendo — and he was installed on the court after denying allegations of sexual assault. While the national environment still favors Democrats by 7.3 percentage points, that’s a 2-point drop since mid-September.

Meanwhile, polls in several key individual races are delivering strong results for Republicans. The most significant movement is coming in North Dakota, where Democratic Sen. Heidi Heitkamp — who voted against Kavanaugh, though her state backed Donald Trump by more than 35 percentage points over Hillary Clinton — looks like an increasingly shaky bet: She now has just a 29.5 percent chance of holding the seat. If Democrats lose even one of their incumbents, such as Heitkamp, they would have to pick up a Southern long shot — Mississippi, Texas or Tennessee — in order to win the Senate.

In Tennessee, Nashville-based pop star Taylor Swift turned heads by endorsing Democrat Phil Bredesen with an Instagram post on Sunday. Republican Marsha Blackburn currently has a 62.8 percent chance of victory, and we will soon find out whether Swift’s bad blood with Blackburn moves the needle.

As part of our extensive on-the-ground coverage of races across the U.S. this year, OZY wanted to build a better product to analyze the national political picture — given the failure of such forecasts in the past. So we decided to team up with Washington-based 0ptimus, a Republican firm that developed an unbiased, nonpartisan prediction model to show its clients in both politics and finance where the winds appear to be blowing.

0ptimus’ data team created and tested countless models, crunching publicly available data against past results in House and Senate races. They take into account more than 100 variables, including past vote totals, generic ballot surveys of which party voters prefer in Congress, the unemployment rate, fundraising data and public polling. The firm developed an artificial intelligence system to “smartly” average together several models to produce the strongest prediction numbers for the 2018 elections, automatically testing against past elections to assess quality. You can read more about the 0ptimus methodology here.

Given the unique factors in 2018, we asked 0ptimus to tweak its calculations, adding weight to:

Gender — women are doing exceptionally well this year, and we expect that trend to continue.

Trump’s approval rating — he hangs over the political and media scene with a heavier presence than past presidents.

Meanwhile, we asked 0ptimus to reduce the weight for:

Candidate ideology — its calculations rewarded more moderate candidates, while we think this election year is all about firing up the base.

Outside money — as OZY has reported, advertising is less persuasive coming from a super PAC than from a candidate.

Because 0ptimus averages several models, it agreed to introduce a new Bayesian model into the mix just for OZY that includes Trump’s approval, gender and unitemized donations while removing one that included ideology and independent expenditures. The result is the numbers we update for you each week.